MEAT, POULTRY, AND EGGS

Humans are omnivores and have historically consumed both plant and animal foods. However,
animals must first meet their own nutritional needs—primarily through consuming plants—
before they can provide meat, milk, or eggs. Direct consumption of plant foods by humans could
support a larger population than animal products, due to greater efficiency in delivering calories
and nutrients.

Despite this, most societies prefer animal foods and are willing to invest more effort and
resources to obtain them. Converting plant-based feed into meat is relatively inefficient (e.g., 2
kg grain/kg chicken, 8 kg/kg beef), affecting food prices.

Animal products are rich in essential nutrients—such as amino acids, vitamins, and minerals—
because human and animal tissues are compositionally similar. While a plant-only diet could
meet human nutritional needs, it would require a wide variety of foods and in-depth nutrition
knowledge. Additionally, farm animals can convert inedible plant materials, like cellulose, into
edible products such as milk, benefiting human diets.

MEAT AND MEAT PRODUCTS

Meat and meat products primarily refer to the skeletal muscles of animals, but also include
organs such as the liver, heart, kidneys, and brain. While poultry and fish are sometimes broadly
considered meat, they are usually categorized separately from red meats like beef, pork, lamb,
and mutton. In the U.S., common meat sources include cattle, hogs, sheep, and calves, whereas
other cultures may consume animals like dogs or kangaroos.

Meat processing also yields valuable by-products, such as intestines for sausage casings, fat for
lard and tallow, hides, wool, bones, blood, gelatin, enzymes, and hormones. As a result, major
meat companies typically engage in multiple product lines beyond just food.

Government Surveillance:

Meat Grading and Inspection

The U.S. meat industry relies on two key government programs:

1. Inspection – Mandatory for all meat and poultry in interstate and intrastate commerce,
focusing on health, safety, and preventing the spread of disease.
2. Grading – Voluntary, used to assess and communicate the quality of meat to buyers and
consumers.

Grading

Grading is important due to the natural variation in meat based on breed, age, feed, and other
factors. It helps ensure quality and consistency in characteristics like:
  Tenderness (based on carcass maturity)
 Marbling (fat distribution)
 Muscle firmness and color

Beef quality grades (from highest to lowest): Prime, Choice, Select, Standard, Commercial,
Utility, Cutter, Canner.
Grades relate to quality, not nutritional value—except in terms of fat content. New ultrasonic
technologies may soon allow quality assessment before slaughter.

Inspection

Meat inspection, governed by the Federal Meat Inspection Act (1906) and enforced by
USDA's FSIS, is mandatory to ensure the meat is:

 Clean, wholesome, and free from diseases or harmful contamination.

 Inspected by veterinarians or supervised personnel during slaughter and processing.

Diseases such as tuberculosis, trichinosis, and salmonellosis can be transmitted through meat,
hence strict inspection laws are in place. Since 1967, all U.S. states must enforce inspection laws
at least as strict as the federal standards.

Slaughtering and Related Practices:

Since 1958, U.S. law requires that animals under federal purchase be rendered insensible to
pain before slaughter, except in religious ritual slaughter. Common humane methods include:

 Stunning with air- or gunpowder-powered devices

 Electric shock
 Carbon dioxide tunnels

These methods may impact the animal’s hormone levels, muscle chemistry, and meat quality.

Slaughter Process

After stunning, animals are hoisted, bled, and moved through an efficient disassembly line in
modern slaughterhouses, where nearly all parts of the animal are used. The carcass is chilled to
2°C within 36 hours to prevent spoilage.

Effect of Stress on Meat Quality

Resting animals before slaughter is important:

 Glycogen in muscles converts to lactic acid after death, lowering pH and preserving
meat.
 Stressed or exercised animals have depleted glycogen, resulting in faster spoilage.
 Stress can also cause meat defects like:
 o Dark-cutting beef
o Pale, soft, watery pork

Structure and Composition of Meat:

 The gross structure of meat includes dark muscle areas and white fat areas, while
microscopic examination shows the detailed muscle structure.
 Lean muscle is made of bundles of muscle fibers, held together by connective tissue
that forms tendons linking muscle to bone.
 Muscle fibers are elongated cells containing myosin (a key protein). Connective tissue
includes:
o Collagen – dissolves into gelatin when cooked with moisture.
o Elastin – tougher, found in ligaments, does not dissolve easily.

Tenderness and Fat Marbling

 Fat marbling (fat between muscle bundles) increases tenderness.

 Thinner fibers, more common in younger animals, are more tender.
 Cooking contracts muscle fibers (can toughen meat) but also:
o Melts fat
o Dissolves collagen into gelatin, improving tenderness

Typical Composition of Beef

 Water: 60%
 Fat: 21%
 Protein: 18%
 Ash (minerals): 1%

Artificial Tenderizing:

1. Natural Tenderization (Ageing)

 Cold room storage allows natural enzymes in the meat to tenderize it over time (known
as ageing or ripening).

2. Mechanical Tenderization

 Hanging carcasses to stretch muscles encourages thinner, more tender fibers.

 Additional methods:
o Pounding or cutting
o Ultrasonic vibration to break muscle fibers

3. Salt and Phosphates

 Salt dissolves proteins:

 o Holds moisture when mixed inside meat (e.g., ground beef)
o Draws moisture out when applied on the surface
 Phosphate salts are even more effective than table salt in tenderizing and retaining
moisture.

4. Enzymatic Tenderization

 Uses proteolytic enzymes like:

o Papain (papaya), bromelin (pineapple), ficin (fig), trypsin (pancreas)
 Methods of application:
o Surface application (limited penetration)
o Injection into meat or into animal before slaughter (more effective)
 Enzymes work until meat reaches ~82°C, after which they are inactivated.

5. Electrical Stimulation

 Latest commercial method.

 100–600 volts applied within 45 minutes of slaughter for 1–2 minutes causes muscle
contractions.
 Benefits:
o Increases tenderness
o Improves meat color, texture, flavor
o Speeds up ageing
 Now used in manual and automatic commercial systems

Curing of Meat:

Meat Curing

Purpose:
Unlike ageing (which mainly improves tenderness), curing serves multiple purposes:

 Preservation
 Flavor enhancement
 Color fixation
 Tenderness improvement

Curing transforms the meat, producing distinct products like:

 Ham
 Bacon
 Corned beef
 Sausages (e.g., bologna, frankfurters)

Historical and Modern Uses

  Historically: Curing was used to preserve meat before refrigeration (as early as 1500
B.C.).
 Today: In developed areas, the focus is more on flavor and color, while in less
developed areas it is still used primarily for preservation.

Color Retention

 Cured meats like corned beef and ham stay red after cooking.
 Uncured meats turn brown when cooked.

Common Curing Ingredients:

1. Sodium chloride (salt): Preserves and adds flavor

2. Sodium nitrate/nitrite: Adds flavor, fixes red color, prevents botulism
3. Sugar: Stabilizes color and adds flavor
4. Spices: Enhance flavor

Note: Nitrates/nitrites are carefully regulated due to safety concerns.

Curing Methods:

 Dry curing: Rubbing ingredients onto the meat or mixing into ground meat
 Wet curing (pickling): Soaking in vats of curing solution
 Injection methods:
o Artery pumping for large cuts (e.g., hams)
o Needle injection for slabs (e.g., bacon)

Meat Pigments and Color Changes:

Understanding meat color is important in meat processing, as it reflects pigment chemistry, not
necessarily freshness or nutritional value.

Main Pigment: Myoglobin

 Myoglobin stores oxygen in muscles.

 Color changes based on oxygen exposure:
o Myoglobin (no oxygen): Purplish (seen in freshly cut meat)
o Oxymyoglobin (oxygenated): Bright cherry red (seen on meat surfaces exposed
to air)
o Metmyoglobin (oxidized): Brown (from prolonged air exposure)

Color and Cooking

 Cooking denatures pigments, turning meat brown.

 Rare steak: More red, less pigment denatured
 Well-done meat: More brown, fully denatured pigments
Cured Meats and Nitrites

 Nitrites bind to myoglobin forming:

o Nitric oxide myoglobin → pink (in uncooked cured meat)
o Nitrosohemochrome → stable pink/red (in cooked ham/bacon)

Factors Affecting Pigment Changes

 Oxygen exposure
 Acidity (pH)
 Light
 These factors influence which pigment dominates.

Packaging Considerations

 Fresh meats: Wrapped in oxygen-permeable films to maintain bright red color.

 Cured meats: Vacuum-packed in oxygen-barrier films to prevent oxidation and color
change.
 Spoilage: Bacterial growth can cause brown, yellow, or green discoloration.

Freezing of Meat:

1. Freezing Durability

 Beef: Can be stored frozen for years

 Pork and fatty meats: Can be stored for months, but oxidized fat flavors may develop
over time

2. Quality Considerations

 Quick freezing is essential for quality.

 Avoid thawing and refreezing, which can cause excessive drip and bleeding.
 Cured meats and sausages are rarely frozen:
o Salt accelerates fat oxidation and rancidity
o Freezing alters seasoning flavors

3. Consumer & Commercial Preferences

 Consumers prefer unfrozen, bright red meat in supermarkets.

 However, they often freeze it at home.
 Restaurants and the military frequently use frozen meat, including imports.

Food Safety: Trichinosis in Pork

 Trichinosis parasite can be killed by:

o Cooking pork to 77°C with a short dwell time
 o Smoking or heating to 58°C
o Freezing pork under USDA-specified time and temperature conditions (see
Table 14.2)

Normal meat inspection may not reliably detect trichina, so USDA safety guidelines are critical
for pork products.

Storage of Fresh Meat:

1. Shift to Centralized Meat Processing

 Supermarket meat cutting is labor-intensive and costly.

 To reduce labor, transport, and storage costs, meat is now often:
o Deboned and trimmed at packing plants
o Cut into primal/subprimal sections (¼ to ⅛ of a carcass)
o Vacuum-packed and shipped to retailers for final cutting
o Repackaged into trays with overwrap for sale

2. Storage and Color Management

 Vacuum-packed beef/pork stored at 0°C (unfrozen) lasts up to 3 weeks.

 In vacuum, meat turns purplish (myoglobin); once unwrapped, it reddens
(oxymyoglobin).
 Alternative method: Pre-cut retail portions wrapped in oxygen-permeable film, then
vacuum-packed as a group. Upon opening, they redden and are shelf-ready.

3. Modified Atmosphere Packaging (MAP)

 A newer, highly effective technology for retail-ready meat.

 Air is replaced with a gas mixture, sealed in high barrier films:
o 10–50% CO₂: Inhibits microbial growth
o 20–50% O₂: Maintains bright red oxymyoglobin color
 Keeps meat fresh, safe, and attractive without additional in-store processing.

Cooking of Meat:

Cooking can either improve or reduce meat tenderness, depending on method and conditions.

Tenderizing Effects:

1. Fat melts → adds moisture and tenderness

2. Collagen dissolves into gelatin → softens connective tissue
3. Muscle fibers separate → improves tenderness

Toughening Effects:
 1. Overheating contracts muscle fibers → meat shrinks and toughens
2. Moisture loss → drying out makes meat tougher

Low-temperature, long-time cooking usually yields more tender meat than high-temperature,
short-time cooking, but effectiveness depends on the meat cut and method used.

Nutritional Impact of Cooking

 Protein and minerals remain largely intact during cooking.

 Some minerals are lost in drippings, but cooking can release calcium from bones.
 B vitamins are heat-sensitive:
o About 70% retained even in well-done meat
o 10% more lost compared to rare meat

Health Trends

 Lower-fat beef and pork are now available due to selective breeding and feeding,
responding to consumer demand for healthier meat options.